Fungi are a group of eukaryotic organisms that include microorganisms such as yeasts, molds, and mushrooms. They are not plants, but rather a separate kingdom of living organisms. Fungi can be single-celled or very complex multicellular organisms and are found in just about any habitat, but most live on land, mainly in soil or on decaying matter.
Fungi are classified based on their life cycles, the presence or structure of their fruiting body, and the arrangement of and type of spores they produce. The three major groups of fungi are:
- Multicellular filamentous molds
- Macroscopic filamentous fungi that form large fruiting bodies, sometimes referred to as "mushrooms"
- Single-celled microscopic yeasts
Molds are made up of very fine threads called hyphae, which grow at the tip and divide repeatedly along their length, creating long and branching chains. The hyphae keep growing and intertwining until they form a network of threads called a mycelium. Digestive enzymes are secreted from the hyphal tip, which break down the organic matter found in the soil into smaller molecules that are used by the fungus.
Fungi are heterotrophs, meaning they acquire their food by absorbing dissolved molecules, typically by secreting digestive enzymes into their environment. They do not photosynthesize. Fungi are among the most widely distributed organisms on Earth and are of great environmental and medical importance. Many fungi are free-living in soil or water, while others form parasitic or symbiotic relationships with plants or animals.
